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300 Six Compression Ratio, Intakes, Heads, etc


Gary Lewis

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Thanks Jon! That's what I figured, but wanted to make sure!

I was looking at the 300/6 engine frame mounts in the LMC catalog, and there sure are a lot of variations. There are different L&R mounts for 1980-1984, then 1985-1988, then the same mount for both left and right from 1989-1993, and then different L&R mounts again for 1994-1996.

If the blocks are basically the same, I guess then that there must also be a few variations of the engine mounts (the mounts between the block and the frame mount(s)?

This is what was causing me to think that there may have been different blocks in the later trucks...

And another question:

There are a couple 300/6 trucks at the local junkyard. One a 1996 f150, and the other I a 1992 F350. The engines are completely intact in both. Unfortunately, like all junkyard stuff, I have no idea on the condition.

Are they easily rebuildable? Usually just typical stuff like any V8 engine with regards to re-bore and crank bearings, etc?

The straight six is a very good rebuild candidate as long as it has not been absolutely clobbered by the previous owner. Because of their zero balance inline design, they wear very evenly. I’ve rebuilt three of them, and none of them had and ridge in the block. My dad’s 240 had about 300K on it when we pulled it and you could still see the cross hatching on all cylinders. It was clattery which was why we decided to rebuild it, but turns out it probably just needed lifters and top end freshening. Of course we went ahead and freshened the whole engine, but it didn’t need to be bored or machined or any of that. With the side cover lifter access, straight row of pistons, and geared timing set they are a pleasure to work on. If you are planning to convert to carb/DSII I would pick whichever truck looks like it was cared for the best. If you think you might want the EFI then the ‘96 SEFI would be nice to have.

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The straight six is a very good rebuild candidate as long as it has not been absolutely clobbered by the previous owner. Because of their zero balance inline design, they wear very evenly. I’ve rebuilt three of them, and none of them had and ridge in the block. My dad’s 240 had about 300K on it when we pulled it and you could still see the cross hatching on all cylinders. It was clattery which was why we decided to rebuild it, but turns out it probably just needed lifters and top end freshening. Of course we went ahead and freshened the whole engine, but it didn’t need to be bored or machined or any of that. With the side cover lifter access, straight row of pistons, and geared timing set they are a pleasure to work on. If you are planning to convert to carb/DSII I would pick whichever truck looks like it was cared for the best. If you think you might want the EFI then the ‘96 SEFI would be nice to have.

The F.I. blocks [1987+] had 2 additional studs for mounting the individual exhaust manifolds. These were to prevent the manifolds from slipping over time since they were not attached to the log intake manifold. Also, the F.I. blocks did not have a mechanical fuel pump.

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The F.I. blocks [1987+] had 2 additional studs for mounting the individual exhaust manifolds. These were to prevent the manifolds from slipping over time since they were not attached to the log intake manifold. Also, the F.I. blocks did not have a mechanical fuel pump.

Not only do they not have a engine mounted mechanical pump, some/most? do not have the hole in the block for said pump. However, the location does have the unthreaded holes for the pump already in the block. You just have to tap the threads and use a fuel pump gasket as a template and cut out the hole for your pump. Or use an electric pump, which I personally don't like them though.

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Yes, but the way the car is, I would be in the line of vision at least half of the time. Maybe I can con one of my neighbors into playing cameraman, then he could apply for a job at CNN.

Couldn't get a cameraman for the Corvair carb adjustment routine. It is finished and awaiting being fetched.

Here is a picture from a FB group, "longroofs, the wonderful world of station wagons" It is the Pontiac 215/230 OHC engine with a factory optional Quadrajet. Note the carburetor orientation, primaries are outboard so mixture distribution is as even as possible.

Pontiac_OHC_6_with_quadrajet.thumb.jpg.dd7372a007f41dfdd2dfda0610357434.jpg

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Couldn't get a cameraman for the Corvair carb adjustment routine. It is finished and awaiting being fetched.

Here is a picture from a FB group, "longroofs, the wonderful world of station wagons" It is the Pontiac 215/230 OHC engine with a factory optional Quadrajet. Note the carburetor orientation, primaries are outboard so mixture distribution is as even as possible.

Glad you got the 'Vair synch'd. Bet it sounded cool.

I remember that Poncho engine. My best friend had the little brother - OHC but no QJet. It ran quite well, but I heard that the ones with the higher compression and the 4bbl ran very well. In fact, about as well as the 326 that was also an option.

I've forgotten what the CFM rating on that little Rochester was. 500? With the tiny primaries that would make a good one for a 300.

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Glad you got the 'Vair synch'd. Bet it sounded cool.

I remember that Poncho engine. My best friend had the little brother - OHC but no QJet. It ran quite well, but I heard that the ones with the higher compression and the 4bbl ran very well. In fact, about as well as the 326 that was also an option.

I've forgotten what the CFM rating on that little Rochester was. 500? With the tiny primaries that would make a good one for a 300.

Yes it does, since it has the dual exhausts it does a passable imitation of a Porsche 911. Considering the 1965-68 Corsa 140s were called the "poor man's Porsche". it is not surprising. Nasty little snarl when you open all 4 carbs.

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Yes it does, since it has the dual exhausts it does a passable imitation of a Porsche 911. Considering the 1965-68 Corsa 140s were called the "poor man's Porsche". it is not surprising. Nasty little snarl when you open all 4 carbs.

I had a fraternity brother in college that had a '65 Corsa, so got to hear that snarl. Loved it! :nabble_smiley_good:

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